From: Michael Wood-Vasey (wmwood-vasey@lbl.gov)
Date: Wed Apr 16 2003 - 09:34:06 PDT
On Wed, Apr 16, 2003 at 11:29:17AM -0500, Robert A. Knop Jr. wrote:
> On Wed, Apr 16, 2003 at 09:25:39AM -0700, Michael Wood-Vasey wrote:
> > BTW, when doing this it's a lot easier to start from the beginning and
> > figure out the z from spectra shifted to the CMB frame rather than
> > apply a correction later. It's the discussion of how to correct
> > already-derived redshifts that makes things confusing.
>
> Not just spectra -- you also have to correct the luminosity distance,
> which is observed in our (geocentric) frame. I was trying to correct
> that by just using a different redshift. Instead, should I figure out a
> Lorentz transformation from the Helio frame to the CMB frame to fix the
> flux, and just use CMB redshifts? That would probably be the right
> thing to do.
Whew. Finally we're on the same page.
Yes, what I've been trying to argue is that you should do everything
from the beginning: Lorentz transform the flux, time, and wavelength.
You're just going to get confused if you try to adjust the derived
values like redshift and luminosity distance.
> Instead, I'm tempted to "just use CMB redshifts" and not mention it,
> because we know nobody will notice (they never have in the past), and
> because we know that these details make no difference except for a
> slight change in alpha and a slight change in the chisquare.
I would rather see us do it completely right.
- Michael
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